Threat processing and PTSD symptom progression over repeated combat deployments.

Background: Psychological reaction to traumatic exposure is heterogeneous and is typically reflected in distinct longitudinal patterns of symptoms development. Various pre-deployment factors have been found to play a role in determining subsequent PTSD symptom trajectories.Objective: Here we delineate the role of threat-related information processing in predicting trajectories of trauma-related PTSD symptom scores conditional on endorsed exposure among combat-deployed infantry soldiers.Methods: A cohort of infantry soldiers (N = 596) was followed over multiple combat deployments to assess the predictive role of baseline threat processing (attention and interpretation) in the trajectories of trauma-related PTSD symptom scores conditional on endorsed exposure. Data were collected at 4-time-points: (1) shortly after enlistment and before deployment; (2) approximately 15 months into service following one deployment; (3) One year later, after further deployments; and (4) another year later, six months following honourable discharge. Behavioural and subjective threat-related attention, and threat interpretation were assessed alongside PTSD symptom severity and traumatic exposure at each time-point.Results: Three distinct symptom trajectories were identified: 'Resilient' (83.7%); 'Worsening' (10.9%), and 'Improving' (5.4%). Elevated subjective attention bias to threat and faster threat interpretation predicted both 'Worsening' and 'Improving' class membership. Notably, while subjective attention bias increased over time across all classes, it was consistently elevated in the non-resilient classes.Conclusions: The results highlight the predictive association between threat processing biases and trajectories of trauma-related PTSD symptom scores conditional on endorsed exposure, offering insights into cognitive mechanisms that may perpetuate or mitigate PTSD symptoms in combat-exposed populations.Trial registration: ClinicalTrials.gov identifier: NCT04651192..